Subtle clues on the 2015 Mustang test mule hint that there are major changes under the 2013 Mustang GT body. The lower rear fascia has been trimmed around the exhaust tips, which could indicate slightly different positioning of the rear mufflers due to a different powertrain or underbody structure. The bulging fuel filler door camouflage suggests a change to the vehicle’s hard points necessitating the relocation of the door. Look closely, and it appears this test mule is also hiding the next-gen Mustang’s independent rear suspension, a much-anticipated change that should put the pony car on more equal footing with the Chevy Camaro and other sports coupes in its category from an overall handling perspective.

The A-pillar gauges also hint that Ford engineers may be monitoring engine vitals such as boost or vacuum pressure, or any number of engine parameters, which would be necessary for an all-new powertrain such as the 3.5-liter EcoBoost V-6. A gap between the roof panel and side panels filled with caulk or putty suggests structural differences above the greenhouse. To compete internationally, Ford knows it needs to downsize the car’s footprint and reduce weight.